Etchant for etching workpieces made of aluminum and aluminum alloys

ABSTRACT

An etchant includes nitric acid (HNO 3 ) having a percentage by mass in the approximate range of 4%-6%, hydrochloric acid (HCl) having a percentage by mass in the approximate range of 1%-3%; and ferric ions (Fe 3+ ) having a concentration in the approximate range of 30-70 grams/liter (g/l). The resultant etchant is suitable for etching aluminum and its alloys. In fact, the etchant is capable of etching such a material to a depth of about 0.1 mm in about 1.8 min, when employed at a temperature in the approximate range of 38° C.-48° C. The etchant further may be recycled, for which an added oxidizer may further be employed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an etchant, and, particularly, to akind of etchant used for etching workpieces made of aluminum or analuminum alloy.

2. Description of Related Art

Workpieces, made of aluminum or an aluminum alloy, are widely used inmodern industry. In use, workpieces made of aluminum or an aluminumalloy are oftentimes etched to form apertures, marks, and/or designs onand/or in surfaces thereof. Generally, a typical etchant includes anacetic acid solution, a hydrochloric acid solution, and a nitric acidsolution. Such an etchant is usually expensive and cannot be recycled.Additionally, when the etchant of this sort is used to etch workpiecesmade of aluminium or an alloy thereof, it usually requires a long timeto etch the workpieces, and it is prone to leave a residue that stainsthe workpieces.

Therefore, a kind of new etchant for etching workpieces made of aluminumor an alloy thereof, is desired in order to overcome the above-describedshortcomings.

SUMMARY

An etchant includes nitric acid having a percentage by mass in anapproximate range from 4% to 6%, hydrochloric acid having a percentageby mass in an approximate range from 1% to 3%; and ferric ions (Fe³⁺)having a concentration in an approximate range of 30-70 grams/liter. Theresultant etchant is suitable for etching aluminum and its alloys.

Other advantages and novel features will become more apparent from thefollowing detailed description.

DETAILED DESCRIPTION OF THE INVENTION

An etchant in accordance with a present embodiment is provided. Theetchant can be applied to workpieces made of aluminum or an aluminumalloy, such as housings of mobile phones, computers, digital cameras,etc., in order to form apertures, marks, and/or designs therein and/orthereon, as the case may be. The etchant is a solution including nitricacid (HNO₃), hydrochloric acid (HCl), and a ferric compound.

In the etchant, the percentage by mass of HNO₃ contained in theresulting etchant is in an approximate range from 4% to 6%, and thepercentage by mass of HCl contained in the resulting etchant is in anapproximate range from 1% to 3%. The ferric (Fe³⁺) compound is a solubleferric compound. Beneficially, the ferric compound can be a ferrichalide chosen from the group consisting of ferric chloride (FeCl₃),ferric bromide (FeBr₃), ferric iodide (FeI₃), and mixtures thereof. Whenthe ferric compound is dissolved in the etchant solution, theconcentration of ferric ions (Fe3⁺) contained in the etchant is in theapproximate range of 30 to 70 grams/liter (g/l).

In preparation of the etchant, HNO₃, HCl, and the aforementioned ferriccompound are mixed in water to form the etchant, wherein an originalpercentage by mass concentration of HNO₃ is about 68%-70%, and anoriginal percentage by mass concentration of HCl is about 30%-32%.Beneficially, in the etchant an optimal percentage by mass of HNO₃ canbe approximately 5%, an optimal percentage by mass of HCl can beapproximately 2%, and an optimal concentration of Fe³⁺ can beapproximately 50 grams/liter (g/l).

In use, the workpieces made of aluminium or aluminium alloy are immersedin the etchant at a temperature in an approximate range of 38° C.-48° C.to be etched. Beneficially, the optimal etching temperature of theetchant is approximately 43° C. When the workpieces are etched by theetchant for about 1.8 minutes, an etching depth in the workpieces isabout 0.1 millimeters (mm). It is to be understood that, for depthsgreater than 0.1 mm, etching times in excess of 1.8 min would be needed,and for depths of less than 0.1 mm, shorter etching times would suffice.After predetermined apertures, marks, and/or designs are formed in/onthe workpieces, the workpieces are taken out from the etchant andcleaned by means of a typical cleaning method, in order to neutralizeand/or remove any etchant remaining thereon upon removal from theetchant.

After the etchant is used, it can be recycled for etching furtherworkpieces. An oxidizer, such as sodium chlorate (NaClO₃) or potassiumchlorate (KClO₃), can advantageously be added into the etchant forresuming/renewing the oxidizing capability of the used etchant.Beneficially, when an oxidation-reduction potential (ORP) of the usedetchant is measured to be less than 550 millivolt (mV), the oxidizershould be added to the used etchant.

Understandably, compared to most kinds of typical etchants, the etchantin accordance with the present embodiment requires less etching time andforms less residue. Additionally, the etchant is less expensive since itcan be recycled.

It is to be further understood that even though numerous characteristicsand advantages of the present embodiments have been set forth in theforegoing description, together with details of structures and functionsof various embodiments, the disclosure is illustrative only, and changesmay be made in detail, especially in matters of shape, size, andarrangement of parts within the principles of the present invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

1. An etchant comprising: a nitric acid (HNO₃) having a percentage bymass in an approximate range of 4%-6%; a hydrochloric acid (HCl) havinga percentage by mass in an approximate range of 1%-3%; and a source offerric ions (Fe³⁺) having a concentration in an approximate range of30-70 grams/liter (g/l).
 2. The etchant as claimed in claim 1, whereinthe percentage by mass of the nitric acid (HNO₃) is approximately 5%. 3.The etchant as claimed in claim 1, wherein the percentage by mass of thehydrochloric acid (HCl) is approximately 2%.
 4. The etchant as claimedin claim 1, wherein the ferric ions (Fe³⁺) have a concentration ofapproximately 50 grams/liter (g/l).
 5. The etchant as claimed in claim1, wherein the etchant is capable of effectively etching aluminum or analloy thereof at a temperature in an approximate range of 38° C.-48° C.6. The etchant as claimed in claim 1, wherein the ferric (Fe3⁺) ions areprovided by a soluble ferric compound dissolved in the etchant.
 7. Theetchant as claimed in claim 6, wherein the ferric compound is chosenfrom the group consisting of ferric chloride (FeCl₃), ferric bromide(FeBr₃), ferric iodide (FeI₃), and a mixture of at least two kinds ofthese kinds of ferric halide.
 8. The etchant as claimed in claim 1,wherein the etchant further includes an oxidizer.
 9. The etchant asclaimed in claim 8, wherein the oxidizer is chosen from the group ofsodium chlorate (NaClO₃) and potassium chlorate (KClO₃).
 10. The etchantas claimed in claim 1, wherein the etchant is capable of etching atleast one of aluminum and an aluminum alloy to a depth of about 0.1 mmin about 1.8 min, when employed at a temperature in the approximaterange of 38° C.-48° C.